# Current Electricity Class 12 MCQ Questions and Answers PDF

Current Electricity Class 12 MCQ is one of the best strategies to prepare for the CBSE Class 12 Board exam. If you want to complete a grasp concept or work on one’s score, there is no method except constant practice. Students can improve their speed and accuracy by doing more MCQ on Current Electricity Class 12 PDF which will help them all through their board test.

## MCQ on Current Electricity Class 12 PDF with Answers

Class 12 Physics MCQ with answers are given here to Current Electricity. These MCQs are based on the latest CBSE board syllabus and relate to the latest Class 12 Physics syllabus. By Solving these Class 12 MCQs, you will be able to analyze all of the concepts quickly in the chapter and get ready for the Class 12 Annual exam.

Learn Current Electricity Class 12 MCQ Questions and Answers PDF download according to the latest CBSE and NCERT syllabus. Students should prepare for the examination by solving CBSE Current Electricity Class 12 MCQ Questions and Answers PDF given below.

Question 1. The electric resistance of a certain wire of iron is R. If its length and radius are both doubled, then
(a) The resistance will be doubled and the specific resistance will be halved
(b) The resistance will be halved and the specific resistance will remain unchanged
(c) The resistance will be halved and the specific resistance will be doubled
(d) The resistance and the specific resistance, will both remain unchanged.

B

Question 2. A heating coil is labelled 100 W, 220 V. The coil is cut in half and the two pieces are joined in parallel to the same source. The energy now liberated per second is
(a) 200 W
(b) 400 W
(c) 25 W
(d) 50 W

B

Question 3. A flow of 107 electrons per second in a conducting wire constitutes a current of
(a) 1.6 × 10–12 A
(b) 1.6 × 1026 A
(c) 1.6 × 10–26 A
(d) 1.6 × 1012 A

A

Question 4. Three copper wires of lengths and cross-sectional areas are (l, A), (2l, A/2) and (l/2, 2A). Resistance is minimum in
(a) wire of cross-sectional area 2A
(b) wire of cross-sectional area A
(c) wire of cross-sectional area A
(d) same in all three cases.

A

Question 5. A 6 volt battery is connected to the terminals of a three metre long wire of uniform thickness and resistance of 100 ohm. The difference of potential between two points on the wire separated by a distance of 50 cm will be
(a) 2 volt
(b) 3 volt
(c) 1 volt
(d) 1.5 volt

C

Question 6. The mean free path of electrons in a metal is 4 × 10–8 m.
The electric field which can give on an average 2 eV energy to an electron in the metal will be in units V/m

(a) 5 × 10–11
(b) 8 × 10–11
(c) 5 × 107
(d) 8 × 107

C

Question 7. The velocity of charge carriers of current (about 1 ampere) in a metal under normal conditions is of the order of
(a) a fraction of mm/sec
(b) velocity of light
(c) several thousand metres/second
(d) a few hundred metres per second

A

Question 8. The resistance of a discharge tube is
(a) non-ohmic
(b) ohmic
(c) zero
(d) both (b) and (c)

A

Question 9. In India electricity is supplied for domestic use at 220 V. It is supplied at 110 V in USA. If the resistance of a 60 W bulb for use in India is R, the resistance of a 60 W bulb for use in USA will be
(a) R
(b) 2R
(c) R/4
(d) R/2

C

Question 10. An electric kettle has two heating coils. When one of the coils is connected to an a.c. source, the water in the kettle boils in 10 minutes. When the other coil is used the water boils in 40 minutes. If both the coils are connected in parallel, the time taken by the same quantity of water to boil will be
(a) 8 minutes
(b) 4 minutes
(c) 25 minutes
(d) 15 minutes

A

Question 11. A charged particle having drift velocity of 7.5 × 10–4 m s–1 in an electric field of 3 × 10–10 V m–1, has a mobility in m2 V–1 s–1 of    B
(a) 2.25 × 1015
(b) 2.5 × 106
(c) 2.5 × 10–6
(d) 2.25 × 10–15

B

Question 12. A carbon resistor of (47 ± 4.7) kW is to be marked with rings of different colours for its identification.
The colour code sequence will be

(a) Violet – Yellow – Orange – Silver
(b) Yellow – Violet – Orange – Silver
(c) Yellow – Green – Violet – Gold
(d) Green – Orange – Violet – Gold

B

Question 13. Fuse wire is a wire of
(a) high resistance and high melting point
(b) high resistance and low melting point
(c) low resistance and low melting point
(d) low resistance and high melting point

B

Question 14. Specific resistance of a conductor increases with
(a) increase in temperature
(b) increase in cross-section area
(c) increase in cross-section and decrease in length
(d) decrease in cross-section area.

A

Question 15. The solids which have the negative temperature coefficient of resistance are
(a) metals
(b) insulators only
(c) semiconductors only
(d) insulators and semiconductors.

D

Question 16. Which of the following acts as a circuit protection device?
(a) fuse
(b) conductor
(c) inductor
(d) switch

A

Question 17. Copper and silicon is cooled from 300 K to 60 K, the specific resistance
(a) decreases in copper but increases in silicon
(b) increases in copper but decreases in silicon
(c) increases in both
(d) decreases in both.

A

Question 18. A wire 50 cm long and 1 mm2 in cross-section carries a current of 4 A when connected to a 2 V battery. The resistivity of the wire is
(a) 4 × 10–6 W m
(b) 1 × 10–6 W m
(c) 2 × 10–7 W m
(d) 5 × 10–7 W m

B

Question 19. A wire of a certain material is stretched slowly by ten percent. Its new resistance and specific resistance become respectively
(a) both remain the same
(b) 1.1 times, 1.1 times
(c) 1.2 times, 1.1 times
(d) 1.21 times, same

D

Question 20. The masses of the wires of copper is in the ratio of 1 : 3 : 5 and their lengths are in the ratio of 5 : 3 : 1. The ratio of their electrical resistance is
(a) 1 : 3 : 5
(b) 5 : 3 : 1
(c) 1 : 25 : 125
(d) 125 : 15 : 1

D

Question 21. Three resistances each of 4 W are connected to form a triangle. The resistance between any two terminals is
(a) 12 W
(b) 2 W
(c) 6 W
(d) 8/3 W

D

Question 22. Two cities are 150 km apart. Electric power is sent from one city to another city through copper wires.     The fall of potential per km is 8 volt and the average resistance per km is 0.5 W. The power loss in the wire is
(a) 19.2 W
(b) 19.2 kW
(c) 19.2 J
(d) 12.2 kW

B

Question 23. A primary cell has an e.m.f. of 1.5 volt. When short-circuited it gives a current of 3 ampere. The internal resistance of the cell is
(a) 4.5 ohm
(b) 2 ohm
(c) 0.5 ohm
(d) (1/4.5) ohm

C

Question 24. A wire of resistance 4 W is stretched to twice its original length. The resistance of stretched wire would be
(a) 8 W
(b) 16 W
(c) 2 W
(d) 4 W

B

Question 25. The drift velocity of the free electrons in a conducting wire carrying a current i is v. If in a wire of the same metal, but of double the radius, the current be 2I, then the drift velocity of the electrons will be
(a) v/4
(b) v/2
(c) v
(d) 4v

B

Question 26. The resistance of a wire is ‘R’ ohm. If it is melted and stretched to ‘n’ times its original length, its new resistance will be
(a) R /n
(b) n2R
(c) R /n2
(d) nR

B

Question 27. Two 220 volt, 100 watt bulbs are connected first in series and then in parallel. Each time the combination is connected to a 220 volt a.c. supply line. The power drawn by the combination in each case respectively will be
(a) 50 watt, 100 watt
(b) 100 watt, 50 watt
(c) 200 watt, 150 watt
(d) 50 watt, 200 watt

D

Question 28. If voltage across a bulb rated 220 volt- 100 watt drops by 2.5% of its rated value, the percentage of the rated value by which the power would decrease is
(a) 20%
(b) 2.5%
(c) 5%
(d) 10%

C

Question 29. Identify the set in which all the three materials are good conductors of electricity.
(a) Cu, Hg and NaCl
(b) Cu, Ge and Hg
(c) Cu, Ag and Au
(d) Cu, Si and diamond

C

Whoever needs to take the CBSE Class 12 Board Exam should look at this MCQ. To the Students who will show up in CBSE Class 12 Physics Board Exams, It is suggested to practice more and more questions. Aside from the sample paper you more likely had solved. These Current Electricity Class 12 MCQ are ready by the subject specialists themselves.

Question 30. An electric kettle takes 4 A current at 220 V. How much time will it take to boil 1 kg of water from temperature 20°C ? The temperature of boiling water is 100°C.
(a) 12.6 min
(b) 4.2 min
(c) 6.3 min
(d) 8.4 min

C

Question 31. Two wires of the same metal have same length, but their cross-sections are in the ratio 3 : 1. They are joined in series. The resistance of thicker wire is 10 W. The total resistance of the combination will be
(a) 40 W
(b) 100 W
(c) (5/2) W
(d) (40/3) W.

A

Question 32. A (100 W, 200 V) bulb is connected to a 160 volts supply. The power consumption would be
(a) 100 W
(b) 125 W
(c) 64 W
(d) 80 W

C

Question 33. A 5°C rise in temperature is observed in a conductor by passing a current. When the current is doubled the rise in temperature will be approximately
(a) 20°C
(b) 16°C
(c) 10°C
(d) 12°C

A

Question 34. An electric bulb is rated 60 W, 220 V. The resistance of its filament is
(a) 870 W
(b) 780 W
(c) 708 W
(d) 807 W

D

Question 35. When a current I is set up in a wire of radius r, the drift velocity is vd. If the same current is set up through a wire of radius 2 r, the drift velocity will be
(a) 4 vd
(b) 2 vd
(c) vd/2
(d) vd/4

D

Question 36. Three copper wires of lengths and cross sectional areas are (l, A), (2 l, A/2) and (l/2, 2A). Resistance is minimum in
(a) wire of cross-sectional area A/2
(b) wire of cross-sectional area A
(c) wire of cross-sectional area 2A
(d) same in all the three cases

C

Question 37. A current of 2 A, passing through a conductor produces 80 J of heat in 10 seconds. The resistance of the conductor in ohm is
(a) 0.5
(b) 2
(c) 4
(d) 20

B

Question 38. A circuit contains an ammeter, a battery of 30 V and a resistance 40.8 ohm all connected in series. If the ammeter has a coil of resistance 480 ohm and a shunt of 20 ohm, the reading in the ammeter will be
(a) 2 A
(b) 1 A
(c) 0.5 A
(d) 0.25 A

C

Question 39. A filament bulb (500 W, 100 V) is to be used in a 230 V main supply. When a resistance R is connected in series, it works perfectly and the bulb consumes 500 W. The value of R is
(a) 230 W
(b) 46 W
(c) 26 W
(d) 13 W

C

Question 40. A 5 ampere fuse wire can withstand a maximum power of 1 watt in the circuit. The resistance of the fuse wire is
(a) 0.04 ohm
(b) 0.2 ohm
(c) 5 ohm
(d) 0.4 ohm

A

Question 41. When a wire of uniform cross-section a, length l and resistance R is bent into a complete circle, resistance between any two of diametrically opposite points will be
(a) R/4
(b) 4R
(c) R/8
(d) R/2

A

Question 42. Resistance n, each of r ohm, when connected in parallel give an equivalent resistance of R ohm. If these resistances were connected in series, the combination would have a resistance in ohms, equal to
(a) n2R
(b) R/n2
(c) R/n
(d) nR

A

Question 43. Two bulbs are of (40 W, 200 V), and (100 W, 200 V). Then correct relation for their resistances is
(a) R40 < R100
(b) R40 > R100
(c) R40 = R100
(d) no relation can be predicted.

B

Question 44. When three identical bulbs of 60 watt, 200 volt rating are connected in series to a 200 volt supply, the power drawn by them will be
(a) 60 watt
(b) 180 watt
(c) 10 watt
(d) 20 watt

D

Question 45. In an household electric circuit, which of the following is / are correct?
(A) All electric appliances drawing power are joined in parallel
(B) A switch may be either in series or in parallel with the appliance which it controls
(C) If a switch is in parallel with an appliance, it will draw power when the switch is in the ‘off’ position (open)
(D) If a switch is in parallel with an appliance, the fuse will blow (burn out) when the switch is put ‘on’ closed.
(a) A, D
(b) A, C, D
(c) B, C, D
(d) A, B, D

B

Question 46. The infinity resistance plug in a post-office box has
(a) an air gap only
(b) a resistance coil of infinite resistance
(c) largest resistance available in box
(d) resistance of the coil 5000 W

A

Question 47. One kilowatt hour is equal to
(a) 36 × 10–5 J
(b) 36 × 10–4 J
(c) 36 × 105 J
(d) 36 × 103

C

Question 48. Three equal resistors connected in series across a source of e.m.f. together dissipate 10 watt of power.    D
What will be the power dissipated in watt if the same resistors are connected in parallel across the same source of e.m.f.?
(a) 30
(b) 10 /3
(c) 10
(d) 90

D

Question 49. If two bulbs, whose resistances are in the ratio of 1 : 2 are connected in series, the power dissipated in them has the ratio of
(a) 2 : 1
(b) 1 : 4
(c) 1 : 1
(d) 1 : 2.

D

Question 50. A 4 mF capacitor is charged to 400 V. If its plates are joined through a resistance of 2 kW, then heat produced in the resistance is
(a) 0.64 J
(b) 1.28 J
(c) 0.16 J
(d) 0.32 J

Question 51. A dynamo develops 0.5 A at 6 V. The energy which is generated in one second is
(a) 0.083 J
(b) 3 J
(c) 12 J
(d) None of these

B

Question 52. If R1 and R2 are the filament resistances of 200 W and a 100 W bulb respectively both designed to run at the same voltage, then
(a) R2 is four times of R1
(b) R1 is four times of R2
(c) R2 is two times of R1
(d) R1 is two times of R2

C

Question 53. If the resistance of a conductor is 5Ω at 50º C & 7Ω at 100º C, then mean temperature coefficient of resistance (of material) is
(a) 0.013/ ºC
(b) 0.004/ ºC
(c) 0.006/ ºC
(d) 0.008/ ºC

A

Question 54. A wire of resistance 12Ω/m is bent to form a complete circle of radius 10 cm. The resistance between its two diametrically opposite points A and B as shown in figure is
(a) 3 Ω
(b) 6 rX
(c) 6 Ω
(d) 0.6 rX

D

Question 55. Two cells of emf ’s approximately 5 V and 10 V are to be accurately compared using a potentiometer of length 400 cm.
(a) The battery that runs the potentiometer should have voltage of 8V.
(b) The battery of potentiometer can have a voltage of 15 V and R adjusted so that the potential drop across the wire slightly exceeds 10 V.
(c) The first portion of 50 cm of wire itself should have a potential drop of 10 V.
(d) Potentiometer is usually used for comparing resistances and not voltages.

B

Question 56. A resistance R is to be measured using a meter bridge. Student chooses the standard resistance S to be 100 Ω. He finds the null point at l1 = 2.9 cm. He is told to attempt to improve the accuracy. Which of the following is a useful way?
(a) He should measure l1 more accurately.
(b) He should change S to 1000 Ω and repeat the experiment.
(c) He should change S to 3 Ω and repeat the experiment.
(d) He should give up hope of a more accurate measurement with a meter bridge.

C

Question 57. What is the equivalent resistance between the points A and D in given figure?

(a) 10 Ω
(b) 20 Ω
(c) 30 Ω
(d) 40 Ω

C

Question 58. Two heating wires of equal length are first connected in series and then in parallel to a constant voltage source. The rate of heat produced in two cases is (parallel to series)
(a) 1 : 4
(b) 4 : 1
(c) 1 : 2
(d) 2 : 1

B

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